fix(custom-model): give a session its own env values back when the selection goes

Applying a custom model writes the endpoint's values over the keys it
injects, and clearing the model unset those keys. A session that had set
one of them itself lost that value: its own DSH_HOME, CODEX_HOME,
GROK_HOME or GEMINI_API_KEY was gone once the model was cleared, and so
was CLAUDE_CONFIG_DIR, which silently moved a Claude session onto the
default account. Switching endpoints did the same.

setCustomModel() now records what the session held under each injected
key and restores it on clear and on switch. Quick-start passes the
caller's values to the Session constructor so they are seen before the
selection lands.

The selection overwrites the only other copy, tmux's setenv, so the
session's own home directory has to survive a Codeman restart on its
own. __customModel therefore stores that one path, the single exception
to persisting keys only, and recovery runs it through
clampEnvOverridesForOwner() so a revoked grant cannot bring it back. Any
other own value, a credential included, stays in memory only.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/web/routes/session-routes.ts

@@ -1689,6 +1689,7 @@ export function registerSessionRoutes(
         envKeys: applied.envKeys,
         configDir: applied.configDir,
         launchModel: applied.launchModel,
+        homeEnvVar: applied.homeEnvVar,
       },
       applied.envOverrides
     );
@@ -4467,12 +4468,12 @@ export function registerSessionRoutes(
     // unknown endpoint, a model id the CLI's argv pattern can't carry) rather than trusting
     // a lighter version of them, since this is the same server-side authority reached a
     // different way, not a separate, less-checked path.
-    let qsCustomModelEnvOverrides = qsGatedEnvOverrides;
-    // Only the INJECTED keys (never the caller's envOverrides merged in) — this is what
-    // setCustomModel() bookkeeping must be given below. The Session constructor already
-    // applies qsCustomModelEnvOverrides (the full merged set) directly; re-merging that
-    // full set into setCustomModel() would put CLAUDE_CODE_EFFORT_LEVEL back after the
-    // constructor stripped it (see setCustomModel()'s own doc comment in session.ts).
+    //
+    // Only the INJECTED keys (never the caller's envOverrides merged in): setCustomModel()
+    // merges these over what the Session constructor took, which is how it learns which of
+    // the caller's values the selection replaced. Handing the constructor the merged set
+    // would hide them, and giving setCustomModel() that set would put
+    // CLAUDE_CODE_EFFORT_LEVEL back after the constructor stripped it.
     let qsCustomModelAppliedEnvOverrides: Record<string, string> | undefined;
     let qsCustomModelLaunchModel: string | undefined;
     let qsCustomModelSessionId: string | undefined;
@@ -4485,6 +4486,7 @@ export function registerSessionRoutes(
           envKeys: string[];
           configDir?: string;
           launchModel?: string;
+          homeEnvVar?: string;
         }
       | undefined;
     if (customModel) {
@@ -4588,7 +4590,6 @@ export function registerSessionRoutes(
       if (!cmApplied) {
         return createErrorResponse(ApiErrorCode.OPERATION_FAILED, `${mode} has no known custom-model mechanism`);
       }
-      qsCustomModelEnvOverrides = { ...qsGatedEnvOverrides, ...cmApplied.envOverrides };
       qsCustomModelAppliedEnvOverrides = cmApplied.envOverrides;
       qsCustomModelLaunchModel = cmApplied.launchModel;
       qsCustomModelBookkeeping = {
@@ -4598,6 +4599,7 @@ export function registerSessionRoutes(
         envKeys: cmApplied.envKeys,
         configDir: cmApplied.configDir,
         launchModel: cmApplied.launchModel,
+        homeEnvVar: cmApplied.homeEnvVar,
       };
 
       // Actually kick off llama-swap's load now — see the dedicated apply route's own
@@ -4630,7 +4632,7 @@ export function registerSessionRoutes(
       copilotConfig: mode === 'copilot' ? qsGatedCopilotConfig : undefined,
       deepSeekConfig: mode === 'deepseek' ? qsGatedDeepSeekConfig : undefined,
       ompConfig: qsResolvedOmpConfig,
-      envOverrides: qsCustomModelEnvOverrides,
+      envOverrides: qsGatedEnvOverrides,
       effort,
       advisorModel,
       remote,
@@ -4659,10 +4661,10 @@ export function registerSessionRoutes(
     const session = new Session(qsSessionOptions);
 
     // Records the selection for session.customModel/getCustomModelForPersist() and future
-    // clear/switch calls — the actual env vars and launch-model config are already part of
-    // the launch above (constructor envOverrides, piConfig/grokConfig/ompConfig.model), so
-    // this is bookkeeping only, never a restart: setCustomModel() is synchronous state, no
-    // tmux IO of its own (see its own doc comment in session.ts).
+    // clear/switch calls, and merges the injected env, which the launch below reads along
+    // with the launch-model config set above (piConfig/grokConfig/ompConfig.model). Nothing
+    // has started yet, so this is never a restart: setCustomModel() is synchronous state,
+    // no tmux IO of its own (see its own doc comment in session.ts).
     if (qsCustomModelBookkeeping) {
       session.setCustomModel(qsCustomModelBookkeeping, qsCustomModelAppliedEnvOverrides);
     }

src/web/server.ts

@@ -104,6 +104,7 @@ import { RunSummaryTracker } from '../run-summary.js';
 import { PlanOrchestrator } from '../plan-orchestrator.js';
 import { OrchestratorLoop } from '../orchestrator-loop.js';
 import { getLifecycleLog } from '../session-lifecycle-log.js';
+import { clampEnvOverridesForOwner } from '../session-env-clamp.js';
 import {
   applyWorkspaceHooks,
   pruneAgentSessionPreambles,
@@ -1532,12 +1533,10 @@ export class WebServer extends EventEmitter {
     }
     try {
       // Boot recovery omits both `workingDir` (no reason to re-answer a trust dialog that
-      // already fired once) and the session-env real-home lookup: the injected VALUES are
-      // never persisted, so after a real restart the session can no longer carry its
-      // allowlisted `DSH_HOME` either (`getEnvOverridesForPersist()` keeps only
-      // `CLAUDE_CODE_*`/`CLAUDE_CONFIG_DIR`): the lookup could only ever hit on the first
-      // apply in-process. Real-home resolution therefore falls back to the SERVER's
-      // `DSH_HOME` or the recipe's `realHomeFallback` (~/.dsh).
+      // already fired once) and the session-env real-home lookup: the first apply already
+      // linked this directory from the session's own home, and `linkRealHomeEntry()` keeps
+      // what is there. Only a directory someone removed gets its links again, from the
+      // SERVER's `DSH_HOME` or the recipe's `realHomeFallback` (~/.dsh).
       return applyCustomModelInjection(
         entry,
         endpoint,
@@ -1559,18 +1558,25 @@ export class WebServer extends EventEmitter {
    * while the new recipe writes one, and clearing it later could then never delete the
    * generated dir. `envKeys` is the UNION of saved and applied keys: the tmux session may
    * still carry `setenv`s from both, and a clear has to unset every one.
+   *
+   * `ownEnv` is always passed, empty for a record saved before it existed: `_envOverrides`
+   * holds what the previous run injected, and only this record says what was the session's
+   * own. It meets the owner's grant again, like every other env override rebuilt from disk.
    */
   private async _restoreCustomModel(session: Session, saved: CustomModelBookkeeping): Promise<void> {
+    const ownEnv = (await clampEnvOverridesForOwner(session.owner, saved.ownEnv)) ?? {};
     const applied = await this._rebuildCustomModelEnv(session, saved);
     if (!applied) {
       // Endpoint gone or CLI unregistered: restore the bookkeeping exactly as saved, which
       // is what a later clear needs.
-      session.setCustomModel(saved);
+      session.setCustomModel({ ...saved, ownEnv });
       return;
     }
     session.setCustomModel(
       {
         ...saved,
+        ownEnv,
+        homeEnvVar: applied.homeEnvVar ?? saved.homeEnvVar,
         // Prefer the current recipe's dir; keep the saved one when the recipe writes none,
         // so a clear can still delete a directory an older recipe created.
         configDir: applied.configDir ?? saved.configDir,